It is desirable for metal parts that are used in a wide variety of applications to have one or more surfaces which have a rough surface texture. For instance, it is desirable for clutch plates, pressure plates, camshaft sprockets, crankshaft sprockets, and a wide variety of other parts to include surfaces which are relatively rough. For instance, parts having at least one rough surface are frequently used in applications where the part is adapted for providing non-rotating engagement with another part in an article of manufacture. In such cases, it is also typically desirable for the rough surface of the part to be surface hardened to provide for better engagement with another part having a softer engagement surface. In other cases, it is desirable for a metal part to have at least one rough surface to facilitate subsequent manufacturing or treatment procedures. For instance, it is important for the metal part used in manufacturing clutch plates to have a friction engagement surface which is relatively rough. This rough surface facilitates subsequent treatment to provide a friction engagement surface having the desired characteristics.
Powder metal parts, such as gears, clutch plates and camshaft sprockets can typically be made at a substantially lower cost than like parts that are made by machining wrought and/or forged steel blanks. For this reason, powder metal parts are widely used in manufacturing consumer products, industrial products, automotive applications, agricultural equipment, heavy equipment, and countless other applications. In some of these applications it is beneficial for one or more sides of the part to have a rough surface. However, providing surfaces on such parts with the desired surface texture can prove to be challenging. In fact, in some cases it is not possible to provide a particular surface on a part with the desired surface texture by conventional techniques, such as grinding, sanding, machining with a rough wheel, cutting, sandblasting, micro-blasting, or shot-peening. The problems associated with providing the surface of a part with a rough surface texture is particularly difficult in cases where the area on the part where a rough surface is desired is obstructed or difficult to reach with conventional roughing methods. In general, it is more difficult to provide a particular surface of a part with a desired rough surface texture in cases where the surface is curved, rounded, tapered, non-uniform, or has a highly detailed surface with multiple surface geometries. Roughening a flat surface on a part by conventional techniques can also prove to be difficult or impossible in cases where the flat surface is obstructed, recessed, or otherwise not readily accessible.
There has been and continues to be a long felt need for a better technique for providing surfaces of powder metal parts with desired rough surface textures. A technique that can apply a desired degree of surface roughness to surfaces that are not readily accessible by conventional techniques and to surfaces which are non-uniform, curved, rounded, tapered, or which have multiple surface geometries would be highly desirable. It would also be highly desirable if such a technique was capable of applying a controlled level of roughness in a relatively uniform manner over the surface of the powder metal part.